1. Field of the Invention
The present invention relates to an embroidery data processing device for processing embroidery data containing positional data representative of needle locations. More particularly, the invention relates to data processing for extracting a contour of an embroidery pattern from the embroidery data.
2. Description of the Related Art
Conventionally, embroidery sewing machines form embroidery patterns on a workpiece cloth based on embroidery data or stitch data. The embroidery data contains positional information about needle locations on the workpiece cloth. Recently, a variety of products with embroidery decorations are sold on the market. For making such products, it is convenient if the size of the embroidery pattern can easily be enlarged or reduced. However, when the size of the embroidery pattern is enlarged merely by increasing the spacing between the needle locations, the thread density becomes low and the base cloth will be seen from the spacing between thread segments. On the other hand, when the size of the embroidery pattern is reduced, the thread segments forming the embroidery pattern are tightly arranged. Such embroidery pattern is difficult to stitch.
One solution for enlarging or reducing the size of an embroidery pattern would be producing block data representative of the contour of the embroidery pattern based on the information about the needle locations contained in the embroidery data. The size of the contour is then changed as desired, and the enlarged or reduced contour is converted back to the positional data in which the needle locations are set on the contour at a predetermined interval so that the resultant embroidery pattern has a predetermined thread density. In actuality, however, converting the positional information into block data is extremely difficult. To date, no technology is available which can perform this conversion with sufficient precision.
Here, an example of a conventional block data technique will be provided. An arc shaped embroidery pattern, such as shown in FIG. 16(b), has an inner side contour R and an outer side contour R'. To insure that the thread density is substantially equal near both the inner and outer sides of the embroidery pattern, half stitch needle locations Q are usually set near the inner side contour R. However, in the conventional block data technique, the half stitch needle locations cannot be distinguished from contour points forming a contour of the embroidery pattern. With such a conventional technique, positional information shown in FIG. 16(a) will result in the block data shown in FIG. 16(b). As such, converting the positional information into block data is not sufficiently precise with the conventional technology.